[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 300238
TCDAT3

Tropical Storm Rina Discussion Number   7
NWS National Hurricane Center Miami FL       AL182023
1100 PM AST Fri Sep 29 2023

Rina continues to produce persistent but poorly organized shower and
thunderstorm activity well to the east of its exposed surface
center. Despite the apparent lack of organization, a pair of ASCAT
passes near 00Z revealed that Rina's wind field was both slightly
larger and stronger than previously estimated. Both ASCAT passes
showed a large swath of winds of 40-45 kt east and northeast of
Rina's center. Based on this new information, the intensity of Rina
has been increased to 45 kt. Both ASCAT passes had slightly higher
winds in the deep convection that were flagged as marginal for
rain contamination, so they weren't considered as representative.
That said, its possible 45 kt could be slightly conservative.

With SHIPS-analyzed 850-200 mb shear higher than 40 kt for the next
24 h, its very unlikely Rina will become any better organized than
it is now. Nearly all of the dynamical models forecast that Rina
will dissipate in the next 24 to 48 h. Based on the structure
information provided by ASCAT, it appears unlikely that the tropical
storm will dissipate that quickly. Therefore the the NHC official
forecast is a little more conservative, but still shows Rina slowly
weakening, close to the intensity consensus. It is worth noting that
the vortex tracker associated with a few models flipped to Philippe
beyond 72 h and the tracks are therefore not representative of the
actual model forecast.

Rina is heading northwestward near 10 kt. The combination of
Tropical Storm Philippe to its west-southwest and a subtropical
ridge to the northeast should keep Rina on this general heading for
a couple of days. The NHC track forecast is near the center of the
guidance envelope, between the simple and corrected consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT  30/0300Z 20.4N  48.8W   45 KT  50 MPH
 12H  30/1200Z 21.1N  50.2W   45 KT  50 MPH
 24H  01/0000Z 22.2N  51.9W   40 KT  45 MPH
 36H  01/1200Z 23.3N  53.7W   35 KT  40 MPH
 48H  02/0000Z 24.8N  55.6W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  02/1200Z 26.7N  56.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  03/0000Z...DISSIPATED

$$
Forecaster D. Zelinsky
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